1. Field of the Invention
The present invention relates to the fields of automation and robotics. Work operations and tasks are carried out by autonomous, self-propelled, self-navigating robots.
2. Related Art
Work operations are under increasing pressure to automate. This is especially true for agricultural operations. Owners of commercial truck farms consisting of fields approximately two to ten acres in size are in special need of a comprehensive, autonomous gardening system to reduce labor costs so as to secure lending and sustain farming as an economically viable land use option.
Automation efforts have proceeded on two fronts: automating work implements and automating guidance of work vehicles. Work implements are effective in performing repetitive tasks such as tillage, planting, fertilizing, cultivating, spraying and harvesting of some kinds of crops. However, effective use of these work implements requires precise guidance of the implement through the field and positioning of the implement in the row, ideally within less than an inch of a target point.
Special challenges arise in determining position with sufficient accuracy in an agricultural context or other work context having a rough topography. A typical farm plot has a rough, undulating or sloping topography which varies depending upon environmental conditions. The position of a self-navigating farm vehicle, and in particular, the position of a work implement thereon, has six degrees of freedom: three-dimensional space, heading, pitch, and roll. Thus, as the inventor discovered, a guidance system for a robot performing precise agricultural work operations must determine position information with respect to six degrees of freedom. A guidance system must determine position information with an accuracy of less than a foot, preferably within one-half inch, even for rough work topographies.
Conventional guidance systems which assume a structured environment allowing only three degrees of freedom, (x, y, heading) such as robots moving in warehouses or on other flat surfaces are not applicable. See, e.g., the automated guided vehicles in U.S. Pat. Nos. 4,119,900; 4,796,198; 4,811,228; 4,817,000; and 5,367,458; and the IEEE article by Yagi et al., "Real-Time Omnidirectional Image Sensor (COPIS) for Vision-Guided Navigation," (each of which is incorporated herein by reference). Designers of these guidance systems face three degrees of freedom and do not encounter the same problems as self-guided systems which move on surfaces that induce tilt.
Global-positioning systems (GPS) have been proposed for self-navigating terrestrial vehicles. To the inventor's knowledge, current commercial GPS positions have an error in the range of 15 meters, although the use of a nearby ground station whose location is known precisely as well as a moving receiver on the vehicle may improve accuracy to within several feet. It remains to be seen whether GPS can effectively and reliably provide position information with an accuracy suitable for controlling agricultural implements in the row. See, e.g., U.S. Pat. Nos. 5,220,876; 5,390,125; 5,438,771; and 5,471,391 (each of which is incorporated herein by reference).
A commercially viable automated farm vehicle must also be simple to operate, durable, and reliable. Scanning systems with mechanical moving parts susceptible to dirt and debris can require frequent servicing. See, e.g., U.S. Pat. Nos. 4,700,301; 4,947,324; 5,008,557; and 5,264,709 (each of which is incorporated herein by reference). Guidance systems requiring specialized survey knowledge for placement of beacons can also be burdensome and commercially limiting for a sole system operator such as a commercial truck gardener. See, e.g., U.S. Pat. Nos. 4,677,555 and 5,477,459 (each of which is incorporated herein by reference).
What is needed then is a precise navigation system and method that detects the position of a self-navigating robot with respect to six degrees of freedom to perform precise work operations over a rough topography. In some applications such as agricultural work operations, a guidance system and method is needed that determines position information with respect to six degrees of freedom with an accuracy of less than a foot, preferably within an inch, even for rough work topographies.
Further, automation of work operations needs to be comprehensive and accessible to farmers of small tracts and solitary operators. A simple system and method is needed for specifying the navigation path to be followed by a self-guided robot through a work area, such as a commercial truck garden plot. Control operations to be performed by the robot along the path must also be easily identified and updated. It is further desirable that information specifying navigation path and control operations to be performed for one crop in a field be able to be preset, saved, modified and exchanged between the self-guided robot and an off-site computer terminal so that a specification can be reused.